1. Field of the Invention
The invention relates generally to the design of circulating valves used in wellbores.
2. Description of the Related Art
Circulating valves are used to provide fluid communication between the central flowbore and the annulus. The typical circulating valve has a sliding sleeve that is movable to selectively cover several ports that allow fluid flow between the annulus and the flowbore. These valves are important during an operation to run a device into a wellbore. They allow fluid to be circulated into the flowbore from the annulus (fill up), or from the flowbore out into the annulus (circulation). They also ensure that pressure is equalized between the flowbore and the annulus. A typical application for a circulating valve would be running in and setting an inflatable packer on coiled tubing. The circulating valve would be open during the run in. When the packer reaches the depth at which it will be set, the circulating valve must be closed in order to set the packer. In conventional designs, surface intervention is necessary to close the valve. Normally, this is accomplished by dropping a closing ball into the flowbore. The ball lands on a ball seat within the valve. Fluid pressure is increased behind the ball, and the sleeve is then shifted closed. On many occasions, including the setting of an inflatable packer, it is undesirable to drop a closing ball to close the sleeve. The operation can be time consuming and detrimental to the operation of tools below the ball. Thus, it is desired to have an alternative method of selectively closing the circulation valve.
The present invention addresses the problems of the prior art.